Charge transport film, material, composition containing same, and electronic device

Abstract

The present disclosure provides a charge transport film, a charge transport material, a composition containing the same, and an electronic device. The charge transport film comprises a polymeric charge transport material, and has a bandgap of 3.0–3.5 eV. The Gaussian standard deviation of the HOMO energy level density of states of the charge transport film, as measured by ultraviolet photoelectron spectroscopy, is σ, which is less than or equal to 0.3 eV. The wide bandgap and low energy disorder of the charge transport material or charge transport film together achieve low electron leakage, thereby improving the efficiency of electronic devices using the charge transport material or charge transport film.

Description

Technical Field

[0001] The present disclosure relates to the field of optoelectronic materials, and more specifically, to a charge transport film, material, composition containing the same, and electronic devices, especially in applications in quantum dot light-emitting diodes. Background Art

[0002] Light-emitting diodes based on solution-processable luminescent materials such as colloidal quantum dots (QDs), conjugated polymers, or metal halide perovskites have the potential to manufacture large-area flexible devices at low cost, making them attractive for next-generation display and lighting technologies. In the past few decades, quantum dot light-emitting diodes (QD-LEDs) have made great progress, achieving high-performance red devices suitable for practical applications. The most advanced red QD-LEDs have high EQE (>20%) and long operating life (1000 cd m -2 T95 at initial brightness, >5000h). However, the electroluminescent efficiency of state-of-the-art green and blue QD-LEDs remains below the theoretical limit defined by the photoluminescent efficiency (PLQY) of the quantum dots used therein. Due to non-ideal operating conditions within the devices, the lifetime of green and blue devices is much lower than that of red QD-LEDs. The commercialization of QD-LEDs requires significant improvements in the performance of green and blue devices. Despite extensive attempts in device engineering and materials screening to reduce the hole injection barrier in QD-LEDs, achieving high-performance green and blue quantum dot LEDs remains challenging. Summary of the Invention

[0003] The purpose of the present disclosure is to provide a charge transport film, material, composition containing the same, and electronic device, which reduce leakage and improve the efficiency of electronic devices using charge transport materials or charge transport films.

[0004] To achieve the above-mentioned objectives, the first aspect of the present disclosure provides a charge transport film, comprising a polymer charge transport material, characterized in that the band gap width of the above-mentioned charge transport film ranges from 3.0 to 3.5 eV, and the Gaussian standard deviation of the HOMO energy level state density distribution of the above-mentioned charge transport film measured by ultraviolet photoelectron spectroscopy is σ, and σ is less than or equal to 0.3 eV.

[0005] Furthermore, the LUMO range of the charge transport film is 0 to -2.3 eV or 0.2 eV shallower than the LUMO of the commercial TFB material film, and the comonomers of the charge transport material are all in a planar configuration.

[0006] Furthermore, the HOMO range of the charge transport film is -5.7 eV to -5.4 eV.

[0007] Furthermore, the density functional theory reformation energy of a monomer of the above-mentioned charge transport material is less than 0.35 eV, or 0.15 eV lower than the density functional theory reformation energy of a monomer of a commercial TFB material.

[0008] A second aspect of the present disclosure provides a charge transport material, wherein the structure of the charge transport material includes Formula A1, and at least one of Formula A2, Formula A3, and Formula A4;

[0009]

[0010] The sum of the molar proportions of the various structures in the structural formula of the above-mentioned charge transport material is 1, and R1 and R2 are independently 1

[0011] R3 and R4 are independently an alkyl group or an aromatic alkyl group having 1 to 20 C atoms.

[0012] Furthermore, the structural formula of the charge transport material is:

[0013] or or or Wherein, x+y=1, and n is an integer greater than or equal to 2.

[0014] Optionally, the structural formula of the charge transport material is:

[0015] or Wherein, x+y+z=1, and n is an integer greater than or equal to 2. In a third aspect of the present disclosure, a composition is provided, comprising any one of the above charge transport materials and at least one organic solvent.

[0016] A fourth aspect of the present disclosure provides an electronic device comprising any one of the charge transport films or charge transport materials described above.

[0017] Furthermore, the above-mentioned electronic device includes at least one of a light-emitting diode, a photovoltaic cell, a light-emitting cell, a field-effect transistor, and a sensor.

[0018] Furthermore, the light-emitting diode is a quantum dot light-emitting diode, the electronic device includes a quantum dot light-emitting layer and a hole transport layer arranged adjacent to the quantum dot light-emitting layer, and the hole transport layer includes the charge transport material.

[0019] Furthermore, the quantum dot light-emitting layer includes quantum dots, and the band gap width of the quantum dots is 1.9-2.7 eV.

[0020] Furthermore, the ratio of the internal quantum efficiency of the quantum dot light-emitting diode to the fluorescence quantum efficiency of the quantum dot light-emitting layer is greater than or equal to 0.9.

[0021] Furthermore, the quantum dot light emitting diodes include at least two of red-band quantum dot light emitting diodes, green-band quantum dot light emitting diodes and blue-band quantum dot light emitting diodes.

[0022] Beneficial effects: The charge transport material or charge transport film with a wider bandgap and low energy disorder jointly achieves low electron leakage, thereby improving the efficiency of electronic devices using the charge transport material or charge transport film. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are intended to explain the present disclosure and do not constitute an improper limitation of the present disclosure. In the accompanying drawings:

[0024] Figure 1 The internal quantum efficiency of the red, green, and blue QD-LED device of the comparative example and the corresponding fluorescence quantum efficiency of the quantum dots are shown.

[0025] Figure 2 The electroluminescence spectra of the red, green and blue QD-LED devices (the curve composed of solid circles) and the electroluminescence spectrum of TFB (the curve composed of hollow circles) are shown.

[0026] Figure 3 The chemical structures, theoretical geometric configurations, and LUMO orbital electronic distributions of TFB (left) and PF8Cz (right) are shown.

[0027] Figure 4 Comparative diagram showing the electronic structures of TFB (left) and PF8Cz (right).

[0028] Figure 5 The UV-visible absorption spectra of TFB and PF8Cz are shown.

[0029] Figure 6 The valence band spectrum obtained by ultraviolet photoelectron spectroscopy (UPS) test and the HOMO state density distribution width obtained by fitting are shown.

[0030] Figure 7 The thickness-dependent surface work function of the HTL material on a Sm substrate or a PEDOT:PSS substrate is shown.

[0031] Figure 8 The results of Example (solid line) and Comparative Example (dashed line) at 100 mA cm -2Electroluminescence spectrum of the green-blue QD-LED device below.

[0032] Figure 9 The current efficiency and power efficiency changes of the green QD-LED (upper figure) and blue QD-LED devices (lower figure) of the embodiment at different voltages are shown.

[0033] Figure 10 The internal quantum efficiency of the green-blue QD-LED device of the embodiment and the corresponding fluorescence quantum efficiency of the quantum dots are shown.

[0034] Figure 11 The EQE variation of the green-blue QD-LED device of the embodiment at different brightness is shown. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0036] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present disclosure are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or are inherent to these processes, methods, products or apparatuses.

[0037] The following describes in more detail exemplary embodiments of the technical solutions provided by the present disclosure. However, these exemplary embodiments can be implemented in a variety of different forms and should not be construed as being limited to the embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of this disclosure thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art.

[0038] Based on traditional energy-level matching principles, researchers generally believe that the biggest problem with blue-green QD-LEDs is hole injection from the hole transport layer (HTL) into the quantum dot layer. The inventors believe that studying the interface between the quantum dot layer and the HTL based solely on traditional energy-level matching theory is overly simplistic and underestimates the electron transfer process from the quantum dot layer to the HTL layer during QD-LED operation, namely electron leakage. The inventors believe that the transfer of electrons from quantum dots to the hole transport material is not only affected by the apparent energy-level matching of the materials, but also by other factors. These factors include the static energy disorder of the HTL, the electron-phonon interaction (dynamic energy disorder), and the geometric structure of the HTL in contact with the quantum dots. The static energy disorder of the HTL stems from a variety of factors, including the diversity of molecular configurations, the distribution of conjugated segment chain lengths, and defect impurities. This broadens the density-of-state (DOS) distribution near the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the polymer film. For typical amorphous conjugated polymer films, the density of states broadened due to energy disorder is usually greater than 0.1eV, indicating that its band tail extends below the LUMO and can accept electron transfer from the quantum dot layer. In addition, due to the flexibility of the organic molecular skeleton, the HTL film has a strong electron-phonon interaction and a large reorganization energy, which will further affect the kinetics of electron transfer. In addition, since a 10-nanometer-sized quantum dot is in contact with multiple HTL units at the same time, the interfacial electron transfer from the quantum dot layer to the HTL is a single-donor-multiple-acceptor process, which will also significantly enhance the probability of electron leakage in the QD-LED.

[0039] The inventors performed quantum chemical calculations on interfacial electron transfer. Theoretical calculations show that for a specific energy barrier, energy disorder and increased HTL reforming can greatly promote electron transfer from quantum dots to HTL. Considering the actual situation of one electron donor (quantum dot) to multiple acceptors (HTL materials) in QD-LEDs, the calculation results show that the probability of electron transfer is significantly increased. Although there seems to be a large energy barrier between the conduction band of quantum dots and the LUMO of HTL materials, the probability of electron transfer calculated by theoretical predictions cannot be ignored. The wider the band gap of quantum dots, the more likely electron leakage occurs, making short-wavelength LEDs more prone to energy loss. The inventors speculate that the electron leakage enhanced by the energy disorder of the material causes significant energy loss in the red, green and blue QD-LEDs of the prior art.

[0040] The first aspect of the present disclosure provides a charge transport film, comprising a polymer charge transport material, wherein the band gap width of the charge transport film is in the range of 3.0-3.5 eV, and the Gaussian standard deviation of the HOMO energy level state density distribution of the charge transport film is measured by ultraviolet photoelectron spectroscopy as σ, and σ is less than or equal to 0.3 eV. σ can characterize the energy disorder. Based on the above theoretical analysis, the smaller σ is, the less electron leakage. The LUMO and HOMO of the charge transport film should be matched and selected according to the actual application, but selecting a charge transport film with a wider band gap width can also reduce electron leakage in electronic devices. In summary, the wide band gap width and low energy disorder work together to achieve low electron leakage, thereby improving the efficiency of electronic devices with charge transport films.

[0041] In some preferred embodiments, the LUMO range of the charge transport film is 0 to -2.3 eV or 0.2 eV shallower than the LUMO of the commercial TFB material (full chemical name: Poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine)) film, and the comonomers of the charge transport material are all planar configurations. By achieving a shallower LUMO energy level (larger band gap) and a more rigid comonomer (lower σ), the efficiency loss pathway of electron leakage due to enhanced energy disorder in QD-LEDs can be suppressed. Based on this new charge transport film, high-efficiency green and blue QD-LEDs can be obtained (because the performance of the red QD-LED in the prior art is already better, it is not emphasized in this article) with minimal luminous efficiency attenuation and a longer working life. The shallower the LUMO of the above-mentioned charge transport film, the better. Commercial TFB materials can be based on the product with SKU number d7eeb22cdb05 (ADS259BE, CAS#223569-31-1) from American Dye Source.

[0042] In some embodiments, the charge transport material is a hole transport material or an electron blocking material.

[0043] In some embodiments, the charge transport film has a HOMO range of -5.7 eV to -5.4 eV.

[0044] In some embodiments, σ ​​is less than or equal to 0.27 eV.

[0045] In some embodiments, the density functional theory reformation energy of a monomer of the charge transport material is less than 0.35 eV, or 0.15 eV lower than the density functional theory reformation energy of a monomer of a commercial TFB material.

[0046] In a second aspect of the present disclosure, a charge transport material is provided, wherein the structural formula of the charge transport material includes A1, and

[0047] At least one structure of Formula A2, Formula A3, or Formula A4;

[0048] The sum of the molar proportions of the various structures in the structural formula of the above-mentioned charge transport material is 1, wherein R1 and R2 are independently alkyl groups having 1 to 20 C atoms, and R3 and R4 are independently alkyl groups or aromatic alkyl groups having 1 to 20 C atoms. The molar proportion refers to the ratio of the amount of substance of A1 or A2 or A3 or A4 in the charge transport material. The charge transport material has a shallower LUMO energy level and a more rigid comonomer (lower σ), which can suppress the efficiency loss pathway of electron leakage in QD-LEDs that is enhanced by energy disorder. Based on this new charge transport material, high-efficiency green and blue QD-LEDs can be obtained, which have minimal luminous efficiency attenuation and a longer working life.

[0049] In some embodiments, the structural formula of the charge transport material includes A1 and A2, or includes A1 and A3, or A1 and A4.

[0050] In some embodiments, the charge transport material has the formula: Among them, x=y=0.5, or x=0.3, y=0.7, or x=0.67, y=0.33, or x=0.83, y=0.17.

[0051] In some embodiments, R1, R2, and R3 are alkyl groups having 4 to 10 C atoms.

[0052] In some embodiments, R1 and R2 are both -C8H 17 Straight chain alkyl, R3 is -C8H 17 Branched chain alkyl.

[0053] In some embodiments, the charge transport material has the structural formula:

[0054] n is an integer greater than or equal to 2.

[0055] In some embodiments, the charge transport material has the formula: or

[0056] Wherein, x+y+z=1, and n is an integer greater than or equal to 2. In some embodiments, x=0.5, y=0.1, z=0.4, or x=0.5, y=0.2, z=0.3.

[0057] In some embodiments, the charge transport material functions as a hole transport material or an electron blocking material.

[0058] In some embodiments, the LUMO range of the charge transport film prepared from the above-mentioned charge transport material is 0 to -2.3 eV, or 0.2 eV shallower than the LUMO of the commercial TFB material (the full chemical name is Poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine)) film, and the comonomers of the charge transport material are all planar. By achieving a shallower LUMO energy level and a more rigid comonomer, the efficiency loss path of electron leakage enhanced by energy disorder in QD-LEDs can be suppressed. Based on this new charge transport material and its film, high-efficiency green and blue QD-LEDs are obtained, which have minimal luminous efficiency decay and a long working life.

[0059] In some embodiments, the HOMO range of the charge transport film is from -5.7 eV to -5.4 eV.

[0060] In some embodiments, the Gaussian standard deviation of the HOMO energy level density of state distribution of the charge transport film measured by ultraviolet photoelectron spectroscopy is σ, and σ is less than or equal to 0.27 eV. σ can represent the energy disorder, so the smaller the better.

[0061] In some embodiments, the density functional theory reformation energy of a monomer of the charge transport material is less than 0.35 eV, or 0.15 eV lower than the density functional theory reformation energy of a monomer of a commercial TFB material.

[0062] According to a second aspect of the present disclosure, a composition is provided, comprising any one of the above charge transport materials and at least one organic solvent.

[0063] The above composition can be prepared to be suitable for printing or coating. In some embodiments, the charge transport material is a hole transport material or an electron blocking material.

[0064] According to a third aspect of the present disclosure, an electronic device is provided, comprising any one of the above-mentioned charge transport films or charge transport materials.

[0065] In some embodiments, the charge transport material is a hole transport material, and the charge transport film is a hole transport film.

[0066] In some embodiments, the electronic device includes at least one of a light-emitting diode, a photovoltaic cell, a light-emitting cell, a field-effect transistor, and a sensor. The electronic device may be a display device. Although this article focuses on light-emitting diodes, the principles can be extended to other optoelectronic devices.

[0067] In some embodiments, the light-emitting diode is a quantum dot light-emitting diode, and the electronic device includes a quantum dot light-emitting layer and a hole transport layer disposed adjacent to the quantum dot light-emitting layer, wherein the hole transport layer includes a charge transport material.

[0068] In some embodiments, the quantum dot light-emitting layer includes quantum dots having a bandgap of 1.9-2.7 eV. The charge transport material or film is particularly suitable for wide-bandgap quantum dots and can improve the performance of quantum dot light-emitting diodes.

[0069] In some embodiments, the quantum dots include one or more of cadmium-free quantum dots and cadmium-containing quantum dots.

[0070] In some embodiments, the ratio of the internal quantum efficiency of a quantum dot light-emitting diode to the fluorescence quantum efficiency of its corresponding quantum dot light-emitting layer is greater than or equal to 0.9. "Corresponding" here refers to the corresponding relationship between the quantum dot light-emitting diode and the quantum dot light-emitting layer contained therein. The fluorescence quantum efficiency of the quantum dot light-emitting layer is tested by coating the quantum dot solution used to prepare the quantum dot light-emitting layer on a blank, transparent substrate and conducting a quantum efficiency test.

[0071] In some embodiments, the quantum dot light emitting diodes include at least two of a red band quantum dot light emitting diode, a green band quantum dot light emitting diode, and a blue band quantum dot light emitting diode.

[0072] In some embodiments, the quantum dot light emitting diode includes a green band quantum dot light emitting diode and / or a blue band quantum dot light emitting diode.

[0073] In some embodiments, the quantum dot light-emitting diode includes a green band quantum dot light-emitting diode, and the ratio of the internal quantum efficiency of the green band quantum dot light-emitting diode to the fluorescence quantum efficiency of the corresponding quantum dot light-emitting layer is greater than or equal to 0.9, or even greater than or equal to 0.95.

[0074] In some embodiments, the quantum dot light-emitting diode includes a red band quantum dot light-emitting diode, and the ratio of the internal quantum efficiency of the red band quantum dot light-emitting diode to the fluorescence quantum efficiency of the corresponding quantum dot light-emitting layer is greater than or equal to 0.9, or even greater than or equal to 0.95.

[0075] In some embodiments, the external quantum efficiency of the quantum dot light emitting diode is greater than or equal to 20%. In some embodiments, the external quantum efficiency of the quantum dot light emitting diode is less than or equal to 25% or 30%. In some embodiments, the green band quantum dot light emitting diode has an external quantum efficiency of 200,000 cd m -2 Under the conditions, the external quantum efficiency is greater than or equal to 20%. In some embodiments, the blue band quantum dot light emitting diode is 25000 cd m -2 Under these conditions, the external quantum efficiency is greater than or equal to 20%. The external quantum efficiency (EQE) mentioned herein refers to the maximum external quantum efficiency, sometimes written as EQE max.

[0076] According to another aspect of the present disclosure, a method for preparing an electronic device is provided, comprising providing a charge transport material to form a charge transport film, wherein the charge transport film has a band gap in the range of 3.0-3.5 eV, and the Gaussian standard deviation of the HOMO energy level density of states of the charge transport film, as measured by ultraviolet photoelectron spectroscopy, is σ, and σ is less than or equal to 0.3 eV. The charge transport film has reduced electron leakage, thereby improving the efficiency of electronic devices using the charge transport film.

[0077] In some embodiments, the charge transport material used in the charge transport film is any of the charge transport materials disclosed herein. In some embodiments, the material of the charge transport film is a hole transport material or an electron transport material.

[0078] Hereinafter, the embodiments are described in more detail with reference to specific examples. However, they are illustrative examples of the present disclosure, and the present disclosure is not limited thereto.

[0079] Chemicals:

[0080] Hydrated zinc acetate (>98%) and hydrated magnesium acetate (99.5%) were purchased from Sigma Aldrich. TFB (average molecular weight, ∼110,000 g / mol) was purchased from American Dye Source. Quantum dots (red CdSe / CdZnSe / ZnS quantum dots, green CdSe / CdZnSe / ZnS quantum dots, and blue CdZnSe / ZnSe quantum dots) were purchased from Nano Crystal Technology Co., Ltd. The surface ligands of all quantum dots were oleate groups. Tetramethylammonium hydroxide (TMAH, 98%) was purchased from Alfa Aesar. Chlorobenzene (ultra-dry solvent, 99.8%), octane (ultra-dry solvent, >99%), and ethanol (ultra-dry solvent, 99.5%) were purchased from Acros. Dimethyl sulfoxide (DMSO, HPLC grade) and ethyl acetate (HPLC grade) were purchased from J&K Chemical Co., Ltd. According to previous reports (Z. Zhang et al, Adv. Mater. 2017, 30, 1801387), colloidal Zn was synthesized by a modified method. 0.85 Mg 0.15 O nanocrystals.

[0081] Example 1

[0082] Preparation of PF8Cz

[0083] Under a nitrogen atmosphere, 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol), 3,6-dibromo-9-(2-ethylhexyl)-carbazole (0.3 mmol), potassium carbonate (2 mmol) and methyltrioctylammonium chloride (A336, one drop) were dissolved in deionized water (1 mL) and toluene (10 mL). After degassing three times, tetrakis(triphenylphosphine)palladium (2 mol%) was added and the mixture was heated to 85 ° C for 24 h. After cooling, the reaction solution was added dropwise to 300 mL of methanol. PF8Cz was filtered and baked under vacuum conditions at 40 ° C. The PF8Cz reaction formula is:

[0084]

[0085] Example 2

[0086] Preparation of PF8Cz33

[0087] The reaction conditions of PF8Cz33 are the same as those of PF8Cz in Example 1. The ratio of the reaction monomers is: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol), 2,7-dibromo-9,9-dioctyl-fluorene (0.1 mmol), and 3,6-dibromo-9-(2-ethylhexyl)-carbazole (0.2 mmol). The reaction formula is as follows:

[0088]

[0089] Example 3

[0090] Preparation of PF8Cz17

[0091] The reaction conditions of PF8Cz17 are the same as those of PF8Cz in Example 1. The ratio of the reaction monomers is: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol), 2,7-dibromo-9,9-dioctyl-fluorene (0.2 mmol), and 3,6-dibromo-9-(2-ethylhexyl)-carbazole (0.1 mmol). The reaction formula is as follows:

[0092]

[0093] Example 4

[0094] Preparation of PF8-27Cz

[0095] The reaction conditions of PF8-Cz27 are the same as those of PF8Cz in Example 1. The ratio of the reaction monomers is: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol) and 2,7-dibromo-9-(2-ethylhexyl)-carbazole (0.3 mmol). The reaction formula is as follows:

[0096]

[0097] Example 5

[0098] Preparation of P36F-27Cz

[0099] The reaction conditions of P36F-27Cz are the same as those of PF8Cz in Example 1. The monomer ratios are: 3,6-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol) and 2,7-dibromo-9-phenyl-carbazole (0.3 mmol). The reaction formula is as follows:

[0100]

[0101] Example 6

[0102] Preparation of P36F-36Cz

[0103] The reaction conditions of P36F-36Cz are the same as those of PF8Cz in Example 1. The monomer ratios are: 3,6-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol) and 3,6-dibromo-9-(2-ethylhexyl)-carbazole (0.3 mmol). The reaction formula is as follows:

[0104]

[0105] Example 7

[0106] Preparation of PF8-CzPh

[0107] The reaction conditions of PF8-CzPh are the same as those of PF8Cz in Example 1. The ratio of the reaction monomers is: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol) and 3,6-dibromo-9-phenyl-carbazole (0.3 mmol). The reaction formula is as follows:

[0108]

[0109] Example 8

[0110] Preparation of PF-DPCz

[0111] The reaction conditions of PF-DPCz are the same as those of PF8Cz in Example 1. The ratio of the reaction monomers is: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol) and N,N-bis(4-bromophenyl)-9-(2-ethylhexyl)-N,N-diphenyl-carbazole-3,6-diamine (0.3 mmol). The reaction formula is as follows:

[0112]

[0113] Example 9

[0114] Preparation of PF-mDPCz

[0115] The reaction conditions of PF-mDPCz are the same as those of PF8Cz in Example 1. The ratio of the reaction monomers is: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol) and N,N-bis(3-bromophenyl)-9-(2-ethylhexyl)-N,N-diphenyl-carbazole-3,6-diamine (0.3 mmol). The reaction formula is as follows:

[0116]

[0117] Example 10

[0118] Preparation of PF-TCz

[0119] The reaction conditions of PF-TCz are the same as those of PF8Cz in Example 1. The ratio of the reaction monomers is: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol) and 3,3″-dibromo-9′-(2-ethylhexyl)-9′H-9,3′:6′,9″-tricarbazole (0.3 mmol). The reaction formula is as follows:

[0120]

[0121] Example 11

[0122] Preparation of PF-2TCz

[0123] The reaction conditions of PF-27TCz are the same as those of PF8Cz in Example 1. The ratio of the reaction monomers is: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol) and 2,2"-dibromo-9'-(2-ethylhexyl)-9'H-9,3':6',9"-tricarbazole (0.3 mmol). The reaction formula is as follows:

[0124]

[0125] Example 12

[0126] Preparation of PF-DPCz-Cz

[0127] The reaction conditions of PF-DPCz-Cz are the same as those of PF8Cz in Example 1. The ratio of the reaction monomers is: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol), N,N-bis(4-bromophenyl)-9-(2-ethylhexyl)-N,N-diphenyl-carbazole-3,6-diamine (0.12 mmol), and 3,6-dibromo-9-(2-ethylhexyl)-carbazole (0.18 mmol). The reaction formula is as follows:

[0128]

[0129] Example 13

[0130] Preparation of PF-TCz-Cz

[0131] The reaction conditions of PF-TCz-Cz are the same as those of PF8Cz in Example 1. The ratio of the reaction monomers is: 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (0.3 mmol), N,N-bis(4-bromophenyl)-9-(2-ethylhexyl)-N,N-diphenyl-carbazole-3,6-diamine (0.06 mmol), and 3,6-dibromo-9-(2-ethylhexyl)-carbazole (0.24 mmol). The reaction formula is as follows:

[0132]

[0133] Example 14

[0134] The device structure of red QD-LED is ITO / PEDOT:PSS / HTL(PF8Cz) / quantum dots / Zn 0.85 Mg 0.15 O / Al. ITO glass (square resistance: 20Ω / sq) was treated with ultrasonic cleaning and oxygen plasma before use. PEDOT:PSS solution (Baytron PVP Al 4083) was spin-coated on the ITO-coated glass at 3000 rpm for 45 s and baked at 150°C for 30 min. PF8Cz solution (12 mg / mL in chlorobenzene) was transferred to a nitrogen-filled glove box (O2<1ppm, H2O<1ppm), spin-coated at 2000 rpm for 45 s, and baked at 150°C for 30 min to form HTL. Quantum dot solution (~15 mg / mL in octane) was spin-coated at 2000 rpm for 30 s. Zn 0.85 Mg 0.15 A solution of O nanocrystals (about 30 mg / mL in ethanol) was spin-coated on the quantum dot layer at 2000 rpm for 45 s and baked at 85 °C. Finally, the solution was heated to 100 °C in a high vacuum (-10 °C). -7 Aluminum electrodes (100 nm) were deposited by thermal evaporation at 100 torr. Before characterization, the device was encapsulated in a glove box using UV-curable resin. The effective size of the QD-LED was 4 mm. 2 .

[0135] Example 15

[0136] The device structure of green QD-LED is ITO / PEDOT:PSS / HTL(PF8Cz) / quantum dots / Zn 0.85 Mg 0.15O / Al. ITO glass (square resistance: 20Ω / sq) was treated with ultrasonic cleaning and oxygen plasma before use. PEDOT:PSS solution (Baytron PVP Al 4083) was spin-coated on the ITO-coated glass at 3000 rpm for 45 s and baked at 150°C for 30 min. PF8Cz solution (8 mg / mL in chlorobenzene) was transferred to a nitrogen-filled glove box (O2<1ppm, H2O<1ppm), spin-coated at 2000 rpm for 45 s, and baked at 150°C for 30 min to form HTL. Quantum dot solution (~15 mg / mL in octane) was spin-coated at 2000 rpm for 30 s. Zn 0.85 Mg 0.15 O nanocrystal solution (about 23 mg / mL in ethanol) was spin-coated on the quantum dot layer at 2500 rpm for 45 s and baked at 85 °C. Finally, the solution was heated under high vacuum (~10 -7 Aluminum electrodes (100 nm) were deposited by thermal evaporation at 100 torr. Before characterization, the device was encapsulated in a glove box using UV-curable resin. The effective size of the QD-LED was 4 mm. 2 .

[0137] Example 16

[0138] The device structure of blue QD-LED is ITO / PEDOT:PSS / HTL(PF8Cz) / quantum dots / Zn 0.85 Mg 0.15 O / Al. ITO glass (square resistance: 40Ω / sq) was treated with ultrasonic cleaning and oxygen plasma before use. PEDOT:PSS solution (Baytron PVP Al 4083) was spin-coated on the ITO-coated glass at 4000 rpm for 45 s and baked at 150°C for 30 min. PF8Cz solution (8 mg / mL in chlorobenzene) was transferred to a nitrogen-filled glove box (O2<1ppm, H2O<1ppm), spin-coated at 2000 rpm for 45 s, and baked at 150°C for 30 min to form HTL. Quantum dot solution (~15 mg / mL in octane) was spin-coated at 2000 rpm for 30 s. Zn 0.85 Mg 0.15 O nanocrystal solution (about 23 mg / mL in ethanol) was spin-coated on the quantum dot layer at 3000 rpm for 45 s and baked at 85 °C. Finally, the solution was heated under high vacuum (~10 -7 Aluminum electrodes (100 nm) were deposited by thermal evaporation at 100 torr. Before characterization, the device was encapsulated in a glove box using UV-curable resin. The effective size of the QD-LED was 4 mm. 2 .

[0139] Comparative Example 1

[0140] The preparation of red QD-LED is the same as that of Example 14, except that the HTL material is changed to TFB.

[0141] Comparative Example 2

[0142] The preparation of green QD-LED is the same as that of Example 15, except that the HTL material is changed to TFB.

[0143] Comparative Example 3

[0144] The preparation of blue QD-LED is the same as that of Example 16, except that the HTL material is changed to TFB.

[0145] Example 17

[0146] Red QD-LED devices were prepared using carrier transport materials PF8-27Cz, PF-DPCz, PF-TCz, and P36F-27Cz as hole transport layers (HTL). The device structure is ITO / PEDOT:PSS / HTL / quantum dots / Zn 0.85 Mg 0.15 O / Al, the device preparation method is consistent with Example 14.

[0147] Example 18

[0148] Blue QD-LED devices were prepared using carrier transport materials PF8-CzPh, PF8Cz33, and PF8Cz17 as HTL. The device structure is ITO / PEDOT:PSS / HTL / quantum dots / Zn 0.85 Mg 0.15 O / Al, the device preparation method is consistent with Example 16.

[0149] Example 19

[0150] Green QD-LED devices were prepared using carrier transport materials P36F-36Cz, PF-mDPCz, PF-2TCz, PF-DPCz-Cz and PF-TCz-Cz as HTL. The device structure is ITO / PEDOT:PSS / HTL / quantum dots / Zn 0.85 Mg 0.15 O / Al, the device preparation method is consistent with Example 15.

[0151] QD-LED Test Method

[0152] The current-voltage luminance characteristics and electroluminescence spectra were measured using a system consisting of a digital source meter (Keithley 2400) and a spectrometer (QE Pro, Ocean Optics) coupled to an integrating sphere (FOIS, Ocean Optics). The absolute spectral radiant flux was calibrated using a radiant flux standard lamp (HL-3plus, Ocean Optics). The standard visual response function (CIE 1931 V(λ)) was used to calculate photometric quantities. The operating lifetime of the QD LED was measured under normal temperature and pressure using an LED lifetime test system from Guangzhou Jinghe Equipment Co., Ltd.

[0153] Optical testing methods

[0154] The absolute PLQY of the quantum dot film was measured using a custom-built integrating sphere coupled to a spectrometer (Ocean Optics, QE65000). The fluorescence decay curve of the quantum dot film was characterized using a steady-state / transient fluorescence spectroscopy system (Dalian Chuangrui Spectroscopy Technology Co., Ltd.), with a picosecond pulsed laser diode (PiLAS) excitation source at a wavelength of 450 nm. The PL spectrum of the HTL film was characterized using a spectrometer (Edinburgh Instruments FLS920) with a xenon lamp as the excitation source. The absorption spectrum of the HTL film was measured using a UV-Vis-NIR spectrophotometer (Agilent Cary-5000).

[0155] UPS testing and energy disorder test methods

[0156] UPS measurements were performed under high vacuum using a Thermo Scientific ESCALAB 250Xi (radiation source: He I21.2 eV). The total DOS width was obtained according to the method reported previously. The total width of the band edge state density, expressed as the Gaussian standard deviation (σ UPS ) is determined by Gaussian fitting of the low energy rising edge of the valence band spectrum. UPS is the inherent energy disorder of the material (σ HOMO ) and instrument broadening factor (σ INS ), By measuring the Fermi edge width of a clean gold substrate, σ INS was determined to be 0.11 eV, which allowed the calculation of the energy disorder of the HTL material (σ HOMO ).

[0157] Surface work function test method

[0158] The surface work function of the HTL film was measured by a Kelvin probe (KP020, KP Technology) in a nitrogen atmosphere. The work function of the probe tip was calibrated with highly ordered pyrolytic graphite (HOPG, work function 4.6 eV).

[0159] Reforming energy calculation method

[0160] DFT calculations of TFB and PF8Cz monomers and dimers were performed with Gaussian 16 at the B3LYP / 6-31G* level. The reformation energy is given by the following formula: λ = E(Q') - E(Q) + E'(Q) - E'(Q'). Where E and E' represent the energies of the neutral and negative point states, respectively, and Q and Q' represent the theoretically optimized configurations of the neutral and negative point states, respectively.

[0161] analyze

[0162] In the QD-LEDs of Comparative Examples 1-3, although the bandgap of the quantum dots widens, the charge injection is still efficient, as shown by the fact that the turn-on voltage of the device is lower than the voltage corresponding to the corresponding photon energy (dashed line). Figure 1 It can be seen that there is a large gap between the internal quantum efficiency (IQE) and the fluorescence quantum yield (PLQY) of the blue-green QD-LED EL. Figure 2 It can be seen that only the electroluminescence of the red QD-LED is pure quantum dot luminescence, which is consistent with the typical quantum dot photoluminescence spectrum. The electroluminescence of the blue-green QD-LED can be seen to have parasitic luminescence of the hole transport material TFB. Since TFB has no quenching effect, the energy transfer of excitons from quantum dots to TFB can be ruled out, indicating that the excitation of TFB comes from the transfer of electrons from quantum dots to TFB. The electroluminescence efficiency of TFB in the above-mentioned device is about 0.01%. Therefore, even the weak TFB luminescence in the blue-green QD-LED of Comparative Examples 2-3 (about 3 orders of magnitude lower than the quantum dot luminescence intensity) indicates that there is a large amount of electron leakage when the QD-LED device is working, which is the reason for the gap between the electroluminescence efficiency of QD-LED and the photoluminescence efficiency of quantum dots.

[0163] The traditional design strategy for improving blue-green QD-LEDs is to deepen the HOMO energy level of the hole transport material. Based on this new understanding of the energy loss mechanism, the inventors proposed a new design strategy for hole transport materials: using copolymer units with a planar configuration and a rigid backbone to achieve a hole transport material with a shallower LUMO energy level and lower energy disorder. The inventors modified the structure of the TFB material to obtain poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(9-(2-ethylhexyl)-carbazole-3,6-diyl)] (PF8Cz for short).

[0164] like Figure 3Compared with the helical triphenylamine groups in TFB, the planar carbazole groups in PF8Cz provide a more rigid framework and potentially more ordered molecular stacking. Correspondingly, PF8Cz has a smaller theoretical reorganization energy, with the theoretical reorganization energies of its dimer and monomer being approximately 0.21 eV and 0.32 eV, respectively; while the theoretical reorganization energies of TFB dimer and monomer are 0.28 eV and 0.47 eV, respectively, indicating that the electron-phonon interaction in PF8Cz is low. In addition, the para-positioned N atom in the 3,6-carbazole group has a strong electron-donating ability and interrupts the conjugation, ensuring a large band gap and a shallow LUMO energy level. The theoretical LUMO of the PF8Cz dimer is 0.24 eV shallower than that of the TFB dimer.

[0165] The characterization of TFB and PF8Cz films confirmed that Figure 4 The required electronic and structural properties of PF8Cz are shown in Figure 1. Compared with TFB film, the absorption spectrum of PF8Cz film shows a blue shift feature and a larger band gap. Among them, the band gap of TFB film measured along the absorption spectrum is 2.88eV, while that of PF8Cz film is 3.06eV. The larger band gap of PF8Cz film is consistent with the PL spectrum characteristics ( Figure 5 ) is consistent. According to the measurement results of the valence band spectrum lift-off of ultraviolet photoelectron spectroscopy, PF8Cz and TFB have the same HOMO energy (-5.4eV) ( Figure 6 ). Combining the test results of band gap width and HOMO energy, it can be seen that compared with TFB, the LUMO energy of PF8Cz is shifted up by 0.2eV ( Figure 4 ), which helps to prevent the electron transfer from the quantum dot conduction band to the LUMO energy level of the organic polymer.

[0166] We can confirm from the HOMO orbital state density distribution and the band bending characteristics of the material that the PF8Cz film has significantly reduced energy disorder compared to the TFB film. In the ultraviolet photoelectron spectrum, the low energy peak width of the valence band spectrum (Gaussian standard deviation σ) characterizes the broadening degree of the material's band edge state density, which is used to evaluate the material's energy disorder. Figure 6 , relative to TFB (σ: 0.37 ± 0.04 eV), PF8Cz shows a steeper rising edge and a narrower peak (Gaussian width, σ: 0.25 ± 0.02 eV), indicating that the PF8Cz film has a lower energy disorder. This result is consistent with the inventors' analysis of the band bending characteristics, that is, the change amplitude of the HTL surface work function (or vacuum energy level) with the increase of the HTL thickness on the conductive substrate. The generation of band bending is attributed to the accumulation of space charges injected into the HTL from the conductive substrate, which has been shown to be directly related to the energy disorder of the polymer. Given that the two HTL films have the same HOMO, PF8Cz in the PEDOT:PSS layer (hollow squares, Figure 7 ) has a smaller surface work function change, that is, the band bending is smaller, reflecting that the HOMO state density of PF8Cz has a narrower distribution.

[0167] In addition, the band bending of PF8Cz on the low work function metal samarium substrate is suppressed (solid squares, Figure 7 ) directly proves that PF8Cz has excellent electron blocking performance, while TFB shows obvious band bending (solid circles, Figure 7 ), originating from the enhanced electron transfer on the Sm side. Finally, by using PF8Cz as the new HTL material, the electroluminescence efficiency of green and blue QD-LEDs was significantly improved. At the same time, the parasitic luminescence of the HTL material in the PF8Cz-based QD-LED was substantially suppressed when compared with the TFB-based device of the comparative example (Regarding the EL characteristics of PF8Cz, Figure 8 This property verifies that the electron blocking properties required by PF8Cz are achieved through effective LUMO orbital energy level control. Due to the good conductivity and suppressed energy loss of QD-LEDs, the green QD-LED device achieved an unprecedented 162 lm W -1 High power efficiency and 127cd A -1 The current efficiency ( Figure 9 The peak IQE of green QD-LEDs (and blue QD-LEDs) is approaching the theoretical limit defined by the PLQY of quantum dot films ( Figure 10 ), indicating that the energy loss channel associated with EL is almost completely suppressed.

[0168] Figure 11 It is worth noting that the green QD-LED has a brightness exceeding 3 orders of magnitude (30 cd m -2 to 200,000 cd m -2 ) range, it shows a wide high efficiency (EQE>20%) window. The EQE of blue QD-LED is 400 cd m -2 to 25000cd m -2 The EQE remains >20% across the entire brightness range.

[0169] Benefiting from the ideal operating conditions within the device, the green and blue QD-LEDs based on PF8Cz have remarkable operating stability. The performance parameters of the QD-LEDs of Examples 14-16 are shown in Tables 1 and 2.

[0170] Meanwhile, red, green, and blue QD-LEDs fabricated using the carrier transport materials prepared in Examples 2-13 as hole transport materials also achieved excellent device performance, as shown in Table 3. The QD-LEDs corresponding to all carrier transport materials generally showed improved performance compared to the comparative examples. While the EQE of the three carrier transport materials in Example 17 was slightly lower than that of Comparative Example 1, they still achieved a relatively high level in the field and could be used as alternatives to existing carrier transport materials.

[0171] Table 1

[0172]

[0173]

[0174] Table 2

[0175]

[0176] Table 3

[0177] hole transport layer EQE max (%) Emitting color Example 17 PF8-27Cz 15.1％ red Example 17 PF-DPCz 18.8％ red Example 17 PF-TCz 20.2％ red Example 17 P36F-27Cz 21.0％ red Example 18 PF8Cz33 20.5％ blue Example 18 PF8Cz17 17.3％ blue Example 18 PF8-CzPh 23.1％ blue Example 19 PF-DPCz-Cz 21.7％ green Example 19 PF-TCz-Cz 24.2％ green Example 19 P36F-36Cz 26.5％ green Example 19 PF-mDPCz 25.6％ green Example 19 PF-2TCz 24.9％ green

[0178] By strategically suppressing potential energy loss pathways for electron leakage in materials enhanced by energy disorder, the disclosed technical solution yields highly efficient green and blue QD-LEDs with minimal efficiency decay and a long operating life, surpassing all previously reported solution-processed QD-LEDs. Given the ubiquity of amorphous charge transport in electroluminescent and other electronic devices, the disclosed technology also provides a universal solution for modulating interfacial charge transfer and improving the performance of various electronic devices.

[0179] The foregoing description is merely a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present disclosure shall be included within the scope of protection of the present disclosure.

Claims

1. An electronic device, characterized in that: The electronic device includes a charge transport film, the charge transport film includes a polymer charge transport material, the band gap width of the charge transport film is in the range of 3.0-3.5 eV, the Gaussian standard deviation of the HOMO energy level state density distribution of the charge transport film is measured by ultraviolet photoelectron spectroscopy, and σ is less than or equal to 0.3 eV. The electronic device is a quantum dot light-emitting diode, the electronic device includes a quantum dot light-emitting layer and a hole transport layer arranged adjacent to the quantum dot light-emitting layer, the hole transport layer includes the charge transport material; the structural formula of the charge transport material is: Wherein, x+y=1, n is an integer greater than or equal to 2; or the structural formula of the charge transport material is: or wherein x+y+z=1, n is an integer greater than or equal to 2; R1 and R2 are independently an alkyl group having 1 to 20 carbon atoms, and R3 and R4 are independently an alkyl group or an aromatic alkyl group having 1 to 20 carbon atoms.

2. The electronic device according to claim 1, wherein The quantum dot light-emitting layer includes quantum dots, and the band gap width of the quantum dots is 1.9-2.7 eV.

3. The electronic device according to claim 1, wherein The ratio of the internal quantum efficiency of the quantum dot light-emitting diode to the fluorescence quantum efficiency of the quantum dot light-emitting layer is greater than or equal to 0.

9.

4. The electronic device according to claim 1, wherein The quantum dot light emitting diodes include at least two of red wavelength quantum dot light emitting diodes, green wavelength quantum dot light emitting diodes and blue wavelength quantum dot light emitting diodes.

5. The electronic device according to claim 1, characterized in that The LUMO range of the charge transport film is 0 to -2.3 eV, or 0.2 eV shallower than the LUMO of a commercial TFB material film, and the comonomers of the charge transport material are all in a planar configuration.

6. The electronic device according to claim 1, characterized in that The HOMO range of the charge transport film is -5.7 eV to -5.4 eV.

7. The electronic device according to claim 1, characterized in that The density functional theory reformation energy of a monomer of the charge transport material is less than 0.35 eV, or 0.15 eV lower than the density functional theory reformation energy of a monomer of a commercial TFB material.

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